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What is a UPS?
A Uninterruptible Power Supply (UPS) is a backup power system that ensures protection to the connected loads in the event of utility power loss.
Whether you are running IT equipment in a data center, hospital, financial center, or any place with critical loads, an interruption in power – even for a few seconds – represents significant losses of money and trust.
A UPS is your first line of defense, immediately delivering power when outages occur – a key difference from other backup power systems like standby generators that require startup time.
How does a UPS Work?
Sustaining a continuous power supply is achieved by providing power from an alternate source – such as batteries – for a pre-determined time (runtime) until either the utility power returns, or the facility can switch to another source such as a generator or fuel cell.
For the crucial period between when the power is lost and the alternate generator starts, the uninterruptible power supply starts within fractions of a second to fill the gap in load, assisting in a smooth and safe transition between the two power sources.
Because the primary purpose of the UPS system is to ensure a seamless and timely transition, reliability is a critical factor in equipment selection.
How do I know if I need a UPS?
Understanding what it costs if your operations were to lose power is vital in determining the value of a UPS to your business.
For businesses where the cost of an outage is minimal and poses little risk to the broader electrical infrastructure, simply using a generator or energy storage system (ESS) may be acceptable.
But for mission critical applications where seconds of downtime per year translate to substantial financial losses, damage to reputations, or safety risks, power availability 99.9999%* of the time is non-negotiable.
Only the most reliable and well-maintained uninterruptible power supply systems can provide this level of dependability.
UPS systems help protect different mission critical facilities from serious disruptions:
- Data Centers — service interruptions could break service-level agreements for uptime with their customers.
- Financial Institutions — missing high-frequency trading and online transactions could result in lost revenue.
- Healthcare Organizations — a power outage or spike can break sensitive medical devices and disrupt critical care for patients.
We’ve answered the question, “What is a UPS?” and why you may need one, so let’s begin to scratch the surface on the technical aspects of these systems.
UPS Voltage Configurations
The two types of voltage configurations are single phase and three phase, with the main difference being as simple as how many power wires are connected to the UPS backup system.
In a single phase, power flows through two wires – a power wire (phase) from the source to the load, which then returns via a neutral wire to the source.
Single phase UPS systems are commonly used for backing up individual computers, standalone IT racks, or other applications with limited load (less than 10kVA).
In a three-phase UPS, there are three power wires (phases) that each carry an alternating current of the same frequency and voltage. Some configurations also include a fourth conductor – the neutral wire -resulting in what is known as a three-phase, four-wire UPS.
Typically, power demands of ~15kVA or more require a larger, 3 phase UPS.
Types of Uninterruptible Power Supply Systems
The three most common types of uninterruptible power supply systems are Standby (offline), Line-Interactive, and Online Double Conversion.
Standby (Offline) UPS
Electrical loads are connected to utility power under normal conditions. If the utility goes down or spikes outside of acceptable voltage, the load switches to UPS power. It is a simple, inexpensive solution for non-critical loads that can live with relatively long outages (2-10 milliseconds) while switching to the UPS.
Line-Interactive UPS
As with the Standby UPS, electrical loads are connected to utility power under normal conditions, but with an additional mechanism to regulate voltage while in the standby mode. Commonly used with small computing servers and networks where power outages present an inconvenience but no substantial financial loss, nor risk to patients in a healthcare setting.
Online Double Conversion UPS
Continuously converts incoming AC to DC and then back to AC, thus completely isolating the load from voltage fluctuations and from the time it takes to transfer power to the batteries.
This makes it the ideal solution for data centers, hospitals, financial centers, and any other application with a critical need for clean, reliable power.
It is common to see single phase voltage configurations in all three types of system design. However, three phase UPS products are commonly online double conversion.
Learn more about the differences between the types of static UPS backup power systems.
Power Conditioning: A Key Benefit of Online UPS Systems
In an ideal world, the electricity from your utility provider would reach your equipment in a perfect waveform—an alternating current (AC) sine wave.
Unfortunately, real-world conditions often disrupt this ideal. Environmental factors such as lightning, ice storms, and wind can distort the waveform.
Combine these with man-made issues like sudden load changes, non-linear loads, and poor maintenance, and you get a compromised sine wave plagued by overvoltage, undervoltage, blackouts, frequency fluctuations, and harmonics.
This is where the power conditioning advantage of an online UPS becomes essential.
A Mitsubishi Electric online double conversion UPS—such as the 9900D, 1100 Series, or 9900AEGIS – does more than provide reliable backup power during outages. They actively filter and stabilize incoming power, delivering clean, consistent, and uninterrupted electricity to your critical systems.
By reducing spikes, surges, and frequency or voltage irregularities, an online UPS protects sensitive equipment from damage and ensures optimal performance.
With Mitsubishi Electric’s online double conversion UPS systems, you’re not just safeguarding against power failures, you’re guaranteeing the highest quality power for your operations.
Think Inside the Box: Key UPS Components
In the mission critical facilities discussed above, the UPS system is central to the critical power infrastructure. Below is a common UPS layout for the data center market: a Mitsubishi Electric 9900D UPS with five Samsung lithium-ion battery racks.
- UPS Power modules feature Insulated Gate Bipolar Transistors (IGBTs), the core power electronics that perform the AC > DC > AC double conversion. AC filter capacitors are also located here, delivering clean waveforms and helping to reduce harmonics.
- The sidecar is where the customer will connect their power cables and batteries.
- Bypass modules allow the UPS to automatically transfer to bypass when a fault is detected.
- Battery cabinets or racks (lithium-ion, VRLA, or Pure Lead) deliver the alternative power source to sustain a continuous power supply until the facility can switch to generator.
Next Steps in Your Critical Power Journey
Selecting an uninterruptible power supply is crucial to protecting your critical infrastructure and ensuring a continuous power supply for your business’s operations. It is a major decision and investment and requires a business to consider many aspects.
Below are a variety of recommended resources that may help on your journey to maximum uptime. And, of course, contact us with any questions or upcoming projects.
- Power Conditioning: More than Just Backup Power
- Minimize UPS Downtime in Critical Power System Design
- What Size UPS Do I Need? The Basics of Sizing a UPS
*In the critical power industry, an availability rating of 99.9999%, referred to as the “six nines,” means that each year there are only 31.56 seconds of downtime.
Edited by Nicole Kristof, Senior Marketing Specialist & Matt Slippy, Marketing Specialist
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